It would have never occurred to me to take a ride in an aqueduct, but now I want to! Before railroads, before highways, Britain built many elevated waterways to transport cargo from place to place. Many are still there, and they are fascinating. Shown is the Pontcysyllte Aqueduct in Wales, which is a UNESCO World Heritage Site and is open for tourist traffic. See ten such UK aqueducts at WebUrbanist. Link

If you need a canal to cross another canal, you simply build a water bridge across, with one canal on top of another. If you need to build a land bridge across a waterway, you can make the bridge split in two or swing aside when tall ships need to pass. But what do you do when you need to have a canal make room for large ships on another canal? That was the situation in Manchester, UK, in 1885. Originally the smaller Bridgewater Canal crossed the Manchester Ship Canal on an arched bridge. But now the region needed to move large ships — too large to fit under the Bridgewater Canal — through the Manchester Ship Canal. So the bridge was replaced with an aqueduct that would swing out of the way of traffic on Manchester Ship Canal:

It was replaced by a unique swing aqueduct that was opened in 1893 and was an even more daring structure than the original aqueduct, consisting of a channel that could be sealed off at each end to form a 235 feet long and 18 feet wide tank, holding 800 tons of water, that swung round on its pivot, situated on an island in the middle of the Ship Canal.

In the links, you can find a video of the swinging aqueduct in action.

Link and Video via The Adventures of Roberta X | Photo: Happy Pontist

UPDATE 11/30/2010: Martin Clark writes with this clarification:

It was not the Manchester Ship Canal that the Bridgewater Canal crossed on an arched bridge – the arched aqueduct actually crossed the Mersey and Irwell Navigation, which was there before the ship canal was built.
The swing aqueduct was built at the same time as the ship canal. The stone arches had been high enough to allow the river barges to pass below, but the sea-going vessels that would use the ship canal were too big, so the swing aqueduct was designed – the first and only one of its kind!

Thanks, Martin!

When they were not too busy conquering distant lands, the Romans liked to dig. German hydromechanics professor Mathias Döring discovered that Roman engineers spent a century digging a 66-miles long underground aqueduct to bring water to modern day Syria:

The soldiers chiseled over 600,000 cubic meters of stone from the ground — or the equivalent of one-quarter of the Great Pyramid of Cheops.

“Over the first 60 kilometers, the tunnel has a gradient of 0.3 per thousand,” explains the project director. That works out to 30 centimeters per kilometer — an astonishingly shallow angle of descent.

Link – via britannica

From the Upcoming ueue, submitted by Minnesotastan.